Referring to FIG. 1, a conventional lens assembly 1 includes a plurality of lens units 11. At least one optical coating is formed on selected ones of the lens units 11 by a film deposition technique so as to control the light transmittance of the lens units 11 at a desired value. However, quality of the optical coating may be adversely affected by unfavorable environmental conditions such as high temperature, high humidity or sudden change in temperature. Under such conditions, the optical coating may lose its structural integrity, peel from the lens units 11, experience change in optical properties or even become malfunctioned. Moreover, owing to the small size of the lens units 11, it is difficult to form the optical coating only on the lens units 11. Portions of the conventional lens assembly 1 other than the lens units 11 may be undesirably coated with the optical coating, thereby resulting in a waste of coating materials.
Referring to FIG. 2, US Patent Application Publication No. 2007/273977 A1 discloses a resin lens unit 2 having a plurality of light-transmissive regions 21 and a plurality of light-shielding regions 22 disposed outside of the light-transmissive regions 21 for removing stray light coming from adjacent light-transmissive regions 21. Since the resin lens unit 2 is used in imaging or illumination applications, the light-shielding regions 22 are not designed to be disposed in the light-transmissive regions 21 so that imaging or illumination qualities are not adversely affected. As such, an optical coating is still required in order to change the light transmittance of the resin lens unit 2 to a desirable value.